Category: Linux

  • apt doesn’t support architecture i386

    After adding facebook hhvm repository on Ubuntu 16.04, i get following error when running “apt update” command.

    root@backup:~# apt-get update
Get:1 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Hit:2 http://us.archive.ubuntu.com/ubuntu xenial InRelease                                                                                                       
Get:3 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB]                                                                                      
Hit:4 http://ftp.osuosl.org/pub/mariadb/repo/10.1/ubuntu xenial InRelease                                                                                        
Ign:5 http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.4 InRelease                                                                                        
Get:6 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease [102 kB]                                                                                    
Hit:7 http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease                   
Hit:8 http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.4 Release             
Ign:10 https://pkg.jenkins.io/debian-stable binary/ InRelease
Hit:11 https://download.docker.com/linux/ubuntu xenial InRelease
Hit:12 https://pkg.jenkins.io/debian-stable binary/ Release
Get:13 https://dl.hhvm.com/ubuntu xenial InRelease [2,411 B]
Get:15 https://dl.hhvm.com/ubuntu xenial/main amd64 Packages [2,244 B]
Fetched 311 kB in 1s (283 kB/s)
Reading package lists... Done
N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://dl.hhvm.com/ubuntu xenial InRelease' doesn't support architecture 'i386'
root@backup:~#

    This is fixed by editing

    vi /etc/apt/sources.list

    Find

    deb https://dl.hhvm.com/ubuntu xenial main

    Replace with

    deb [arch=amd64] https://dl.hhvm.com/ubuntu xenial main

  • add-apt-repository

    add-apt-repository command can be used to add repository in ubuntu.

    To install, run

    apt-get install software-properties-common python-software-properties

    Example

    apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 0xB4112585D386EB94
add-apt-repository https://dl.hhvm.com/ubuntu

  • rsync

    rsync command with exclude option, full server backup to a remote server.

    rsync -avz --progress --human-readable "-e ssh -p 3333" --exclude /backup --exclude /proc --exclude /sys / root@REMOTE_SERVER_IP:/backup/serverX/

    Transfer a file

    I normally use scp to do single file transfer. It may be better to it with rsync as you will be able to resume.

    rsync -P -e ssh root@SERVER_IP:/path/to/file.tar.gz /local/path/

    -P == –partial –progress

    If you use non standard SSH port, then replace -e ssh with “-e ssh -p PORT_NUMBER”.

    Example

    boby@hon-pc-01:~$ rsync -P "-e ssh -p 3333" root@s12:/home/cloud-architect.tar.bz2 /backup/learn/cloud-architect.tar.bz2
  3,120,159,768 100%  995.98kB/s    0:36:27 (xfr#1, to-chk=0/1)
boby@hon-pc-01:~$

    See backup

  • smartctl

    To check hard disk for errors, run

    /usr/sbin/smartctl -q errorsonly -H -l selftest -l error /dev/sda

    Here is an example of HDD with errors

    # smartctl -q errorsonly -H -l selftest -l error /dev/sda
ATA Error Count: 8259 (device log contains only the most recent five errors)
Error 8259 occurred at disk power-on lifetime: 8324 hours (346 days + 20 hours)
Error 8258 occurred at disk power-on lifetime: 8324 hours (346 days + 20 hours)
Error 8257 occurred at disk power-on lifetime: 8324 hours (346 days + 20 hours)
Error 8256 occurred at disk power-on lifetime: 8324 hours (346 days + 20 hours)
Error 8255 occurred at disk power-on lifetime: 8324 hours (346 days + 20 hours)

#

    To get detailed, result, run

    smartctl -a -d ata /dev/sda

    hdd

  • gzip

    Enable Gzip in Amazon Linux
    How to enable gzip on Plesk Nginx

    To check if a web site have gzip enabled, run

    curl -I -H 'Accept-Encoding: gzip,deflate' https://YOUR_DOMAIN.EXTN

    When you have no GZIP enabled, you will see error as follows

    boby@hon-pc-01:~$ curl -I -H 'Accept-Encoding: gzip,deflate' https://serverok.in
curl: (7) Failed to connect to serverok.in port 443: Connection refused
boby@hon-pc-01:~$

    With gzip enabled, you see something like following

    boby@hon-pc-01:~$ curl -I -H 'Accept-Encoding: gzip,deflate' https://serverok.in
HTTP/1.1 200 OK
Server: nginx/1.10.3 (Ubuntu)
Date: Sat, 23 Dec 2017 16:53:49 GMT
Content-Type: text/html; charset=UTF-8
Connection: keep-alive
Link: ; rel="https://api.w.org/"
Link: ; rel=shortlink
Strict-Transport-Security: max-age=31536000; includeSubDomains
Content-Encoding: gzip

boby@hon-pc-01:~$

    To enable gzip on nginx web server, i added following to server block

    gzip          on;
gzip_comp_level     5;
gzip_min_length     256;
gzip_types
    application/atom+xml
    application/javascript
    application/json
    application/rss+xml
    application/vnd.ms-fontobject
    application/x-font-ttf
    application/x-font-opentype
    application/x-font-truetype
    application/x-javascript
    application/x-web-app-manifest+json
    application/xhtml+xml
    application/xml
    font/eot
    font/opentype
    font/otf
    image/svg+xml
    image/x-icon
    image/vnd.microsoft.icon
    text/css
    text/plain
    text/javascript
    text/x-component;
gzip_disable  "MSIE [1-6]\.(?!.*SV1)";

  • systemctl

    Service files

    To list all services run

    systemctl -a

    List all enabled services

    systemctl list-unit-files | grep enabled

    See all running services

    systemctl | grep running

    See see dependency for a package, run

    systemctl list-dependencies --reverse PACKAGE_NAME

    systemctl list-dependencies

    Service file location

    service files are located in /usr/lib/systemd/system

    [root@web-0001 system]# pwd
/usr/lib/systemd/system
[root@web-0001 system]# ls -l | grep php
-rw-r--r--  1 root root  507 Jul  6  2017 php56-php-fpm.service
-rw-r--r--  1 root root  502 Jan  3 06:55 php72-php-fpm.service
-rw-r--r--  1 root root  467 Jun  7  2017 php-fpm.service
[root@web-0001 system]#

    Systemd unit types

    systemctl -t help
systemctl -t timer
systemctl -t service

  • Install shadowsocks on Ubuntu

    Install ShadowSocks server on Debian 10
    install ShadowSocks client in Ubuntu 18.04

    On the Server, install shadowsocks with

    apt install python-pip python-m2crypto
pip install shadowsocks

    Create config file for server

    vi /etc/shadowsocks.json

    Add

    {
"server":"SERVER_IP",
"server_port":8044,
"local_port":0,
"password":"PASSWORD",
"timeout":600,
"method":"aes-256-cfb"
}

    Replace SERVER_IP and PASSWORD in above config. Start server with

    ssserver -c /etc/shadowsocks.json -d start

    Example

    root@backup:~# ssserver -c /etc/shadowsocks.json -d start
INFO: loading config from /etc/shadowsocks.json
2017-12-23 03:46:57 INFO     loading libcrypto from libcrypto.so.1.1
started
root@backup:~#

    Shadowsocks client

    Shadowsocks have clients for different operating systems. Some are GUI. On Ubuntu, i install CLI version, that is part of shadowsocks server. To install run

    apt install shadowsocks

    Now start the sslocal program with command

    sudo ss-local -s server_address -p server_port -l local_port -k password -m encryption_method

    Example

    sudo /usr/bin/sslocal -s 188.11.131.92 -p 4545 -l 7070 -k KVhXq@JkNuH4h -m aes-256-cfb

    Now you will be able to configure your browser to use socks proxy listing at 127.0.0.1:7070

  • Monitor redis with redis-cli

    On Ununtu/Debian, install it with

    apt -y install redis-tools

    To get stats, run

    redis-cli --stat

    If your redis on differnt sevrer or use non standard port, then use

    redis-cli -h HOSTNAME -p PORT --stat

    Example

    root@ip-10-0-0-31:~# redis-cli -h news24redis.cylrbg.0001.use1.cache.amazonaws.com --stat
------- data ------ --------------------- load -------------------- - child -
keys       mem      clients blocked requests            connections          
9287       20.58M   27      0       179271 (+0)         1208        
9287       20.62M   27      0       179277 (+6)         1208        
9288       20.67M   28      0       179377 (+100)       1209        
9288       20.64M   28      0       179494 (+117)       1209        
9292       20.71M   28      0       179823 (+329)       1210        
9292       20.68M   28      0       179969 (+146)       1211        
9298       20.74M   29      0       180033 (+64)        1212        
9311       20.67M   28      0       180162 (+129)       1214        
9314       20.69M   29      0       180198 (+36)        1215        
9318       20.80M   30      0       180275 (+77)        1216        
9318       20.68M   30      0       180280 (+5)         1216        
9318       20.82M   31      0       180307 (+27)        1218        
9319       20.74M   31      0       180321 (+14)        1218        
9322       20.70M   29      0       180350 (+29)        1219        
9324       20.80M   30      0       180377 (+27)        1220        
9366       20.90M   30      0       180724 (+347)       1221        
9368       20.77M   29      0       181086 (+362)       1221        
9368       20.73M   27      0       181133 (+47)        1221        
9372       20.73M   27      0       181487 (+354)       1222        
9380       20.73M   27      0       181592 (+105)       1223        
------- data ------ --------------------- load -------------------- - child -
keys       mem      clients blocked requests            connections          
9384       20.76M   28      0       181639 (+47)        1224        
9391       20.77M   28      0       181718 (+79)        1224        
9391       20.79M   27      0       181731 (+13)        1224        
9391       20.67M   25      0       181771 (+40)        1224        
9391       20.67M   25      0       181780 (+9)         1224        
9391       20.67M   25      0       181849 (+69)        1224        
^C
root@ip-10-0-0-31:~#

    INFO

    redis-cli INFO

    If you want to see info about clients, run

    redis-cli INFO clients

    Monitor

    To see what redis is doing, run

    redis-cli monitor

    If your redis is running on remote server, then use

    redis-cli -h REMOTE_SERVER_IP monitor

  • Connect to redis from PHP

    To connect to redis, first install php-redis

    apt install php-redis

    Now create a php file with following code

    root@ip-10-0-0-31:/var/www/html# cat 2.php 
connect('news24redis.cylrbg.serverok.use1.cache.amazonaws.com', 6379); 

echo "Connection to server sucessfully"; 

echo "Server is running: ".$redis->ping(); 
root@ip-10-0-0-31:/var/www/html#

    redis

  • Install Redis PHP module in Ubuntu 16.04

    To install redis php module in Ubuntu 16.04, run

    apt -y install php-redis

    If you are using Apache, restart Apache.

    systemctl restart apache2

    If php-fpm restart

    systemctl restart php7.0-fpm

    You will see following in your phpinfo()

    php redis

  • redis

    Install Redis

    Install latest Redis on Ubuntu/Debian Server
    Install Redis on Plesk Debian Server
    Install Redis from Source

    How Tos

    Installing Redis PHP module CentOS 7
    Connect to redis from PHP
    Monitor redis with redis-cli
    redis commander – Web GUI for Redis
    How to find Redis data directory
    How to flush Redis cache
    Redis error currently not able to persist on disk

    Checking if Redis works

    # telnet 127.0.0.1 6379
set testkey 10
get testkey

    Example

    root@ip-10-0-0-31:~# telnet news24redis.cylrbg.0001.use1.cache.amazonaws.com 6379
Trying 10.0.0.223...
Connected to news24redis.cylrbg.0001.use1.cache.amazonaws.com.
Escape character is '^]'.
set testkey 10
+OK
get testkey
$2
10
quit
+OK
Connection closed by foreign host.
root@ip-10-0-0-31:~#

    Count Number of Keys

    To count number of keys, use

    DBSIZE

    Example

    root@ip-10-0-0-31:~# telnet news24redis.cylrbg.0001.use1.cache.amazonaws.com 6379
Trying 10.0.0.223...
Connected to news24redis.cylrbg.0001.use1.cache.amazonaws.com.
Escape character is '^]'.
DBSIZE
:4114

    Here DBSIZE returned 4114, that means you have that much key/value stored in redis.

    Flush ALl

    To flush all keys, use

    redis-cli flushall

  • composer

    composer is PHP package manager, to install, run

    curl -sS https://getcomposer.org/installer |  php -- --install-dir=/usr/local/bin --filename=composer

    Install Packages

    Run this every time you change composer.json or pull newer copy from git.

    composer install

    Show Installed Packages

    composer show -i

    Update Software

    Only run this if you need to update software versions. Don’t run it in production. Only run when you are project maintainer and need everyone else use latest version of packages.

    composer update